I. Field of the Invention
This invention relates to the protection of piping and in particular of fuel piping against lightning in aircrafts with a composite structure and to achieve this, it proposes a connection device for aircrafts fuel piping that comprises end fittings with suitable resistivity.
II. Description of Related Art
In aircrafts, the path of fuel tubing is complex and requires many changes of direction; this requires making connection parts between tubes with diverse geometry.
In addition, in the case of aircrafts with fuselage and wings of composite material, the conductivity of the structure is much lower than that of the paths of metal tubes and because of this, a very large part of lightning currents pass through these paths.
In theory, degradation of these paths may occur when there is excessive current.
To limit the passage of lightning currents, parts that are insulating or more resistive than the structure must be added to the piping that makes up these paths.
It is, nevertheless, necessary to evacuate the electrostatic charges that can accumulate in the piping.
This is all the more necessary when the piping is located in a fuel tank.
Current metal piping in particular is fitted with welded or crimped, male or female metal connectors and comprises bonding tabs welded onto the tube.
In a composite structure airplane, for example with a carbon fiber structure, the piping is usually manufactured either in highly resistive materials or metal (Aluminum, Titanium, Stainless Steel). The connectors are generally manufactured in aluminum.
Current composite piping is fitted with bonded metal connectors that comprise metallization tabs, which are bonded or added when the tube is manufactured. The metal connector also comprises metallization tabs i.e. tabs for receiving a grounding metal braid called “metallization braid”.
For machined or molded connectors, the male or female end fittings are machined.
Existing solutions to solve the problems involve adding insulating elements between 2 pieces of piping and grounding the insulated sections.
It is known to cut off the electrical path along the piping and, in particular, document EP 0 297 990 A1 proposes cutting the electrical path by making tubes at least partly from electrically insulating material; document EP 2 034 228 A1 describes the use of insulating insertions between the tubes; document EP 0 217 313 describes insulating tubes one from the other and grounding some tubes.
In summary, to respond to the constraints of eliminating electrostatic charges while limiting the passage of the lightning currents, metal tubing is not resistive enough and must be sectioned, thermoplastic materials alone are too resistive which limits the allowable length of piping.
To solve the above problem, document FR2 948 254 A1 by the applicant provides for alternating metal connection parts and insulating connection parts. This configuration requires connectors between tubes with complex geometry; in addition, these connectors must be made in different materials.